Field theory reformulated without self-energy parts

Abstract

The intuitive description of atomic levels requires the use of renormalized objects, with lifetime and dressed atomic levels. The reformulation of field theory for avoiding self-energy parts in the dynamical evolution enables us to provide such a description outside the scope of the usual quantum mechanics. That approach is illustrated here on a two-level system, interacting with a field, inside and outside the rotating wave approximation (RWA). A kinetic extension of the description is reached, enabling a statistical mixture to change its composition with time. The original reversible description is embedded in the new one and is recovered now from a restricted class of initial conditions. After dressing, the structure of the kinetic operators inside and outside the RWA is now common.